Evaluation of absolute form measurements using a tilted-wave interferometer

Fortmeier, Ines; Stavridis, Manuel; Wiegmann, Axel; Schulz, Michael; Elster, Clemens

doi:10.1364/oe.24.003393

Cited by 35 publications

(26 citation statements)

References 8 publications

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“…It has been shown by Fortmeier et al in simulations that the absolute reconstruction of TWI can be further improved by adding an absolute path length, e.g., with a synthetic wavelength. 39 This will be the subject of future investigations. In this context, Fizeau-interferometry is advantageous.…”

Section: Discussionmentioning

confidence: 93%

Measuring aspheres quickly: tilted wave interferometry

Pruß

Baer²,

Schindler

2017

Opt. Eng

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Abstract. Functional surfaces with a rising degree of complexity are becoming increasingly important for modern industrial products. It is common knowledge that one cannot produce surfaces better than it is possible to measure them. Consequently, the demand for their effective and precise measurement has increased to the same extent as their production capabilities have grown. Important classes of optical functional surfaces are aspheres and freeforms. Both types of surfaces have become essential parts of modern optical systems such as laser focusing heads, sensors, telescopes, glasses, head-mounted displays, cameras, lithography steppers, and pickup heads. For all of them, the systematic quality control in the process of their fabrication is essential. We review the challenges of asphere and freeform testing and how available metrology systems cope with it. A special focus is on tilted wave interferometry and how it compares to other methods. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Discussionmentioning

confidence: 93%

Measuring aspheres quickly: tilted wave interferometry

Pruß

Baer²,

Schindler

2017

Opt. Eng

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“…TWI is trying to realize absolute form metrology with traceable uncertainties in combination with virtual experiments. [ 62 ] However, a fixed microlens array generates test wavefronts with fixed tilts, which still limits its flexibility in measuring freeform surfaces. To address this problem, a tip/tilt mirror was proposed to scan subapertures with flexible angle compensation [ 63 ] at the cost of sacrificing the inherently parallel sampling of TWI.…”

Section: Interferometric Areal Measurementmentioning

confidence: 99%

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

Chen

Xue

Zhai

et al. 2020

Laser & Photonics Reviews

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Freeform optical surfaces are advantageous to optical designers, as they provide additional degrees of freedom for optimization. The loss of rotational symmetry, however, makes measurement of freeforms more challenging. Herein, advances in interferometric areal measurement of freeform optical surfaces, including null tests, non-null tests, near-null tests, and adaptive null tests, are reviewed. Some new developments, in the Hartmann test, deflectometry, and phase retrieval, as representatives of non-interferometric areal measurement, are then presented. Overall, the focus is on single-point-probe-based profilometry categorized into coordinate measurements and slope-or curvature-based measurements. Innovative measurement technology is trying to bridge the gap between high accuracy and high dynamic range as freeform optical surfaces are finding more applications in visible and shorter-wavelength optics.

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“…The TWI is a special full-field interferometric measurement device for measuring the form of aspherical and freeform surfaces. [13][14][15][16][17] It combines a special noncommon path setup with ray tracing and model-based evaluation procedures to determine the form of such surfaces. The basic setup is shown in Fig.…”

Section: Measurement Systemmentioning

confidence: 99%

“…[13][14][15][16][17] Furthermore, a beam stop in the Fourier plane of the imaging optics limits the fringe density at the detector and avoids subsampling effects. [13][14][15][16][17] With this setup, depending on the local slope of the specimen, several small subinterferograms ("patches") are generated at the detector. To avoid interference from the light of adjacent light sources, only every second light source in each row and column of the source array is switched on at the same time.…”

Section: Measurement Systemmentioning

confidence: 99%

“…To avoid interference from the light of adjacent light sources, only every second light source in each row and column of the source array is switched on at the same time. [13][14][15][16][17] Therefore, four camera images are needed to obtain the data covering the whole SUT. The number and size of the patches generated depend on the form of the SUT and on its measurement position.…”

Section: Measurement Systemmentioning

confidence: 99%

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Traceability of form measurements of freeform surfaces: metrological reference surfaces

2019

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Due to the complexity of measurement systems for asphere and freeform surfaces, well-known artifacts are required to characterize the accuracy of the results of their form measurements. We present advancements in manufacturing and characterization of metrological multispherical freeform artifacts. The strong cooperation between the manufacturing and measurement units of Physikalisch-Technische Bundesanstalt (PTB) allows the form of the artifacts to be manufactured very accurately and the root-meansquare deviation from the desired design form to be improved by a factor of >20 compared to former results (e.g., from a value >500 nm to about 20 nm). Furthermore, a nickel/phosphorous coating is added to the copper surface, resulting in greater hardness and allowing the coated surface to be used as a reference for low-force tactile measurement systems. Four Gaussian peak fiducial marker structures are added to the design to improve the evaluation of comparison measurements. In addition to characterizing the radii in the spherical segments using PTB's radius measurement bench, we also characterize the sphericity of the spherical segments using a Fizeau interferometer. We show form measurement results for a full-field measuring tilted-wave interferometer and compare the form measurement results in the spherical segments with measurement results obtained with the Fizeau interferometer.

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Evaluation of absolute form measurements using a tilted-wave interferometer

Cited by 35 publications

References 8 publications

Measuring aspheres quickly: tilted wave interferometry

Measuring aspheres quickly: tilted wave interferometry

Measurement of Freeform Optical Surfaces: Trade‐Off between Accuracy and Dynamic Range

Traceability of form measurements of freeform surfaces: metrological reference surfaces

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